This invention relates to lids for containers, and specifically to a lid adapted to provide an increased degree of flexibility in operative flanges thereon, whereby the lid is less susceptible to inadvertent dislodgement from an associated container, and the ease of installation and removal of the lid with respect to such a container is improved without foregoing the necessary and desirable sealing and shape-retention properties of the lid and container.
To prevent undesired denting, bending, or other deformation, prior art lids sometimes include flanges with reinforcing ribs. These ribs typically render the flanges (and correspondingly the lid) relatively stiff and inflexible by virtue of the orientation of the reinforcing ribs perpendicularly to the flange, thereby preventing or resisting deflection of the flange in that direction.
The development or evolution of this prior art rib and flange configuration may find its roots in the utilization of injection molding processes and materials for forming such containers and lids. The desire for "stiffness" may have arisen from the need to market the injection-molded containers against metallic or other acceptably "tough" containers. The perpendicular reinforcement ribbing accomplishes the aforedescribed stiffening purpose, thereby persuading customers that the plastic containers may be suitably interchanged with and utilized instead of metallic or other containers. Additionally, the perpendicular orientation of the reinforcing ribs may permit easier removal of the lids from the forming molds, in comparison to more complex configurations.
Although the perpendicular ribs achieve the desirable stiffening of flanges, they also contribute to the undesired "popping off" of the lid when a container is inadvertently dropped or knocked over. Because the side of the container is typically not reinforced, it may be relatively flexible and may therefore deform when dropped (especially when filled with a heavy commodity). The relatively inflexible lid on the container (due at least in part to the perpendicular reinforcing ribs) prevents the lid from correspondingly deforming, resulting in dissociation of the lid from the container and the spillage of the contents thereof.
In addition, the lack of flexibility of such prior art reinforced flanges can increase the effort required to install and remove the lid from an associated container. Where, for example, such a flange forms one or more side walls of a groove or channel for receiving an interengaging edge of such a container, and where such desired interengagement requires or would be aided by temporary deflection of such flange or flanges, the energy required to seat the lid on the container can be considerable. Similar considerations apply to removal of the lid from the container.
Moreover, the inflexible nature of the prior art flanges is relatively exacting in automated lidding processes. Misalignment of the flange with respect to the opening of a corresponding container tends to result in breakage of the container or lid, or at least non-seating of the lid, when automated machinery attempt to seat the lid on the container.